Quantiles revision

Quantiles· A quan/le is a sta/s/c that measures a certain propor/on of the waythrough a set of data. They are measures of spread (dispersion).·To find different quan/les in a set of data, use the followingmethod; Find the number of items in a set of data (take this to be n) Mul/ply n by the relevant frac/on in the table. Quan/le Example Frac/on Quar&les Q1 (Lower Quar/le) ¼ Q2 (Median) ½ Q3 (Upper Quar/le) ¾ Deciles D1 ... D9 1/ 10 e.g. D3 3/ 10 Percen&les P1 ... P99 1/ 100 e.g. P70 70/ 100 CAUTION for all Quan&les Ø If the answer is a WHOLE NUMBER then take the mean of this piece of data and the next e.g. find the mean of the 7th and 8th pieces of data. Ø If the answer is NOT A WHOLE NUMBER, ALWAYS ROUND UP e.g. 3.36 è4th piece of data. · RANGE ­ Maximum Value - Minimum Value · IQR (Interquar&le Range) ­ Q3 - Q1 · SIQR (Semi-Interquar&le Range) ­ Q3 - Q1 2